The present invention relates generally to lancet devices and relates more particularly to a novel lancet device.
There are many medical conditions for which it is desirable to draw a blood sample from a patient for analysis. For example, in the case of certain communicable diseases, a blood sample drawn from a patient may be analyzed for the presence of a blood borne pathogen. Alternatively, in the case of diabetes, blood samples drawn periodically from a patient may be used to monitor blood sugar levels.
Blood samples taken from a patient for blood sugar monitoring are typically obtained by piercing the skin of the patient using a lancet device. A lancet device typically includes a body and a lancet. The body is typically adapted to be held by the user, the lancet being coupled to the body and being adapted to pierce the skin of the patient so as to draw blood therefrom. In some lancet devices, the lancet extends from the body at all times. As can readily be appreciated, such lancet devices may inadvertently prick people and/or become contaminated with foreign objects and, therefore, pose a safety risk. Accordingly, in other lancet devices, the lancet is adapted to be moved, when actuated, from a retracted position in which the lancet tip is disposed within the body to an extended position in which the lancet tip extends beyond the body. Typically, the movement of the lancet from its retracted position to its extended position is effected with such force that contact of the moving lancet tip with the skin of a patient results in the piercing of the skin of the patient. In many such lancet devices having a movable lancet, the lancet is automatically drawn back into the body after reaching its extended position in order to minimize the risk of inadvertent lancet sticks.
Lancet devices having a movable lancet typically fall into one of two types. In one such type of device, the lancet is, prior to use and without any prepping by a user, maintained in an armed state, ready to be fired. The firing of a lancet in such a device is typically effected either by pressing or compressing the entire device against the skin of the patient or by depressing a movable plunger or trigger on the device while holding the remainder of the device against the skin of the patient. Examples of the aforementioned type of lancet device are disclosed in the following documents, all of which are incorporated herein by reference: U.S. Pat. No. 5,201,324, inventor Swierczek, issued Apr. 13, 1993; U.S. Pat. No. 5,540,709, inventor Ramel, issued Jul. 30, 1996; U.S. Pat. No. 5,709,699, inventor Warner, issued Jan. 20, 1998; U.S. Pat. No. 5,755,733, inventor Morita, issued May 26, 1998; U.S. Pat. No. 6,322,574, inventors Lloyd et al., issued Nov. 27, 2001; U.S. Pat. No. 6,358,265, inventors Thorne, Jr. et al., issued Mar. 19, 2002; and U.S. Patent Application Publication No. US 2002/0087180, inventors Searle et al., published Jul. 4, 2002.
One drawback to lancet devices of the type described above is that such devices require the user, who is typically also the patient whose skin is about to be pricked, to provide the necessary force to drive the lancet through the skin of the patient. Because most people have an aversion to being pricked, there is a natural tendency for the patient to flinch before or as the lancet is moving, with the result that a clean piercing is often not achieved. Moreover, because an inexperienced patient often will not know the appropriate amount of force necessary to drive the lancet through the skin, it is not uncommon for such a patient to fail to insert the lancet through the skin, with the result that the procedure must be repeated.
Another drawback to lancet devices of the type described above is that it is possible for the lancet to be fired prematurely simply by the inadvertent application of pressure to the lancet device. As can readily be appreciated, the premature firing of the lancet may result in an undesired piercing of a person and/or in the contamination of the lancet. In addition, with respect to those lancet devices that also include a safety feature for preventing the lancet from being used multiple times, the premature firing of the lancet will prevent the lancet device from later being used for its intended purpose. Furthermore, for those lancet devices that do not include a safety feature for preventing the lancet from being used multiple times, even if the lancet is not fired prematurely and is, in fact, used on its intended patient, there is a risk that subsequent handling of the lancet device by a second person may result in an inadvertent lancet stick of said second person.
The second type of lancet device having a movable lancet typically takes the form of a pen-shaped device comprising a spring-loaded lancet, cocking means for storing energy in the spring, and trigger means for releasing the energy stored in the spring to drive movement of the lancet. In use, the spring is cocked, the device is held against the skin of the patient, and the trigger is fired. Examples of the aforementioned type of lancet device are disclosed in the following documents, all of which are incorporated herein by reference: U.S. Pat. No. 4,462,405, inventor Ehrlich, issued Jul. 31, 1984; U.S. Pat. No. 4,503,856, inventor Cornell et al., issued Mar. 12, 1985; U.S. Reissue Pat. No. 32,922, inventors Levin et al., reissued May 16, 1989; U.S. Pat. No. 5,613,978, inventor Harding, issued Mar. 25, 1997; and U.S. Patent Application Publication No. U.S. 2001/0027326, inventor Schraga, published Oct. 4, 2001.
Of the above documents, U.S. Reissue Pat. No. 32,922 is illustrative. In this patent, there is disclosed a lancet device comprising an inner tubular member and an outer tubular member, the inner tubular member being telescopically mounted within the outer tubular member. A lancet holder is slidably mounted within the inner tubular member, the lancet holder receiving at its forward end a lancet. A shaft extends rearwardly from the lancet holder, the shaft traveling through the inner tubular member and terminating within the outer tubular member. A spring is mounted on the shaft within the inner tubular member, the spring biasing the lancet holder forwardly. A finger formed on the lancet holder is adapted to extend radially outwardly through a transverse opening in the inner tubular member. A trigger mounted externally to the inner tubular member is adapted to engage the lancet holder finger and to push said finger into the inner tubular member through the transverse opening. To cock the device, the outer tubular member is pulled away from the inner tubular member and then released. The pulling away of the outer tubular member causes the shaft to be pulled rearwardly and the spring to be compressed. In addition, the pulling away of the outer tubular member causes the finger on the lancet holder to be drawn into the transverse opening in the inner tubular member, thereby retaining the spring in its compressed state. To fire the device, the trigger is depressed. Depression of the trigger causes the finger to be pushed back into the inner tubular member, thereby releasing the spring. Said release of the spring results in the lancet being driven forwardly through the end of the inner tubular member. After firing, a second spring, which is located in the outer tubular member surrounding the rear end of the shaft, draws the lancet back into the inner tubular member.
One drawback to the aforementioned lancet device is that one must use two hands to cock the device, one hand to hold the inner tubular member and the other hand to pull the outer tubular member rearwardly relative to the inner tubular member. In addition, after cocking the device, one must re-position the hand that is going to be used to fire the device so that a finger is positioned over the trigger.
Another drawback to the aforementioned lancet device and to many of the other lancet devices described above is that such devices are intended to be used to prick the finger tip of a patient (the finger tip being highly vascularized) and then to have the patient express a drop of blood from the pricked finger tip. This can be problematic, however, since the finger tip has a high concentration of pain receptors located therein. Consequently, both the act of pricking the finger tip and the act of expressing blood therefrom can be quite painful. Moreover, this effect is magnified where the patient is diabetic, and frequent blood samples must be drawn. This problem cannot simply be avoided by using the same devices on alternate body parts, such as the forearm, the trunk, the buttocks and the upper thighs, which do not have as high a concentration of pain receptors as the finger tips, since these devices are not designed to draw an adequate amount of blood for sampling from these less vascularized body parts.